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1. Introduction：Weld neck flanges are visually different from other flange types by their long tapered hub and smooth transition of thickness up to where the butt weld joins to a pipe or a fitting.
2. Description: A weld neck flange (WN flange) means a flange has a neck for weld with the pipe, it is easily to recognized by their long tapered neck on the flange (The neck is also called hub in the weld neck flange). The tapered neck can supply a high strength reinforcement to support flange and pipe. It means the weld neck flange is suitable to be used in high pressure and extremely temperature situation.
| Nominal Pipe Size | Outside Diameter (O) | Thickness (T) | Raised Face Diameter (R) | Length Thru Hub (Y) | Point of Weld (A) | Hub Diameter (X) | Bore (B) | Approximate Weight (lbs) | Bolt Circle (C) | Number of Holes | Diameter of Holes |
| 1/2 | 3.75 | 0.56 | 1.38 | 2.06 | 0.84 | 1.5 | 0.62 | 2 | 2.63 | 4 | 0.63 |
| 3/4 | 4.63 | 0.63 | 1.69 | 2.25 | 1.05 | 1.88 | 0.82 | 3 | 3.25 | 4 | 0.75 |
| 1 | 4.88 | 0.69 | 2 | 2.44 | 1.32 | 2.13 | 1.05 | 4 | 3.5 | 4 | 0.75 |
| 1 1/4 | 5.25 | 0.75 | 2.5 | 2.56 | 1.66 | 2.5 | 1.38 | 5 | 3.88 | 4 | 0.75 |
| 1 1/2 | 6.13 | 0.81 | 2.88 | 2.69 | 1.9 | 2.75 | 1.61 | 7 | 4.5 | 4 | 0.88 |
| 2 | 6.5 | 0.88 | 3.63 | 2.75 | 2.38 | 3.31 | 2.07 | 9 | 5 | 8 | 0.75 |
| 2 1/2 | 7.5 | 1 | 4.13 | 3 | 2.88 | 3.94 | 2.47 | 12 | 5.88 | 8 | 0.88 |
| 3 | 8.25 | 1.13 | 5 | 3.13 | 3.5 | 4.63 | 3.07 | 15 | 6.63 | 8 | 0.88 |
| 3 1/2 | 9 | 1.19 | 5.5 | 3.19 | 4 | 5.25 | 3.55 | 18 | 7.25 | 8 | 0.88 |
| 4 | 10 | 1.25 | 6.19 | 3.38 | 4.5 | 5.75 | 4.03 | 25 | 7.88 | 8 | 0.88 |
| 5 | 11 | 1.38 | 7.31 | 3.88 | 5.56 | 7 | 5.05 | 32 | 9.25 | 8 | 0.88 |
| 6 | 12.5 | 1.44 | 8.5 | 3.88 | 6.63 | 8.13 | 6.07 | 42 | 10.63 | 12 | 0.88 |
| 8 | 15 | 1.63 | 10.63 | 4.38 | 8.63 | 10.25 | 7.98 | 67 | 13 | 12 | 1 |
| 10 | 17.5 | 1.88 | 12.75 | 4.63 | 10.75 | 12.63 | 10.02 | 91 | 15.25 | 16 | 1.13 |
| 12 | 20.5 | 2 | 15 | 5.13 | 12.75 | 14.75 | 12 | 140 | 17.75 | 16 | 1.25 |
| 14 | 23 | 2.13 | 16.25 | 5.63 | 14 | 16.75 | 13.25 | 180 | 20.25 | 20 | 1.25 |
| 16 | 25.5 | 2.25 | 18.5 | 5.75 | 16 | 19 | 15.25 | 250 | 22.5 | 20 | 1.38 |
| 18 | 28 | 2.38 | 21 | 6.25 | 18 | 21 | 17.25 | 320 | 24.75 | 24 | 1.38 |
| 20 | 30.5 | 2.5 | 23 | 6.38 | 20 | 23.13 | 19.25 | 400 | 27 | 24 | 1.38 |
| 22 | 33 | 2.63 | 25.25 | 6.5 | 22 | 25.25 | 21.25 | 465 | 29.25 | 24 | 1.63 |
| 24 | 36 | 2.75 | 27.25 | 6.63 | 24 | 27.63 | 23.25 | 580 | 32 | 24 | 1.63 |
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